it seems the kernel source tar ball has been lost, and the build tool attempt to fetch it from git tree.

In the SDK 1.2 release for e500v2 platform, there are 2 ISOs released, QorIQ-SDK-V1.2-SOURCE-20120614-yocto.iso and QorIQ-SDK-V1.2-PPCE500V2-20120614-yocto.iso, the former one contains the source files, recipes, and documents, the latter one contains binary to accelerate the building, please make sure you have installed both of them.